This invention is in the field of devices for magnifying and projecting a picture image from a television set. Several devices have heretofore been designed and marketed for magnifying and projecting a picture image from a cathode ray tube of a television set onto a remotely located screen. Many of the early devices were very expensive and thus could be justified only for commercial use. More recently, devices have been marketed costing several thousand dollars and designed for use either in a small business or residential setting. For example, a projection color television system marketed by Advent Corporation of Cambridge, Massachusetts projects three separate color pictures simultaneously onto a concave configured screen which then displays the composite color picture. The distance between the viewing surface and the projector is particularly critical in the Advent system. Such a system is not designed to be added onto an existing television set but instead includes a built-in receiver.
Other devices for magnifying and projecting a television picture image include different types of housings attachable to a television set with different types of lenses and mirrors provided in the housing for the projection and magnification. A kit is sold by the Macrocoma Company which necessitates positioning the television set in an inverted position with the picture image then being directed through a right angle housing and reflected off a mirror within the housing through a flat lens movable to and from the housing. The brightness of the projected image on the viewing surface is critical in order to provide a satisfactory picture to the viewer. Mirrors do not reflect 100% of the image received and thus considerably reduce the brightness of the projected image. As a result, systems utilizing mirrors are particularly disadvantageous for color picture projection.
Convex and/or concave configured lenses are utilized in some television set projectors in lieu of the flat lens. For example, a device sold by Extron Ltd., 8833 Sunset Boulevard, West Hollywood, Calif. 90069, includes a straight housing mountable to a television set with an aperture provided at the opposite end of the housing to receive a barrel-configured lens including a pair of double convex lens between which is positioned a double concave lens. Such a barrel-type lens is manufactured by U.S. Precision Lens, 3997 McMann Road, Cincinnati, Ohio 45245, under the name "Beta-II-Lens."
A number of U.S. patents have been granted on a variety of devices for projecting a television picture image. For example, U.S. Pat. No. 4,051,535 issued to James M. Inglis includes a housing mountable to a television set having at the end opposite the television screen a flat lens through which the image is projected and magnified. Another approach is shown in U.S. Pat. No. 3,820,885 issued to Bennie S. Miller which uses a standard overhead projection unit to reflect and then magnify the picture image.